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You'll need to edit either E3SM/components/$component/bld/configure OR E3SM/components/$component/cime_config/buildlib_cmake and make a PR to merge your change.
Permanently change compiler flags for a component or entire build (How to use our CMake macro system!)
CMake macros are loaded in this order. If the macro doesn't exist, that level is skipped. Users will usually be working with the $compiler_$mach.cmake macro.
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